High-fidelity, low-latency polarization quantum state transmissions over a hollow-core conjoined-tube fibre at around 800 nm

TL;DR

This paper demonstrates high-fidelity, low-latency polarization-encoded quantum state transmission over a novel hollow-core fibre, overcoming previous limitations in modal purity and loss for quantum communication at around 800 nm.

Contribution

It introduces a conjoined-tube hollow-core fibre that achieves reliable, high-quality quantum photon transmission with minimal polarization degradation and low latency, suitable for advanced quantum information applications.

Findings

Achieved ~0.98 fidelity in single-photon transmission

Demonstrated low latency transmission at ~99.96% speed of light

Realized high spatial mode purity and low polarization degradation

Abstract

The performances of optical fibre-based quantum information systems are limited by the intrinsic properties of silica glass materials, e.g. high latency, Rayleigh-scattering loss wavelength scaling law, and cross-coupling induced modal impurity. Hollow-core optical fibre (HCF) promises to unify air-borne light propagation and non-line-of-sight transmission, thus holding great potentials for versatile photonics-based quantum infor-mation applications. The early version of HCF based on photonic-bandgap guidance has not proven itself as a reliable quantum channel because of the poor modal purity in both spatial and polarization domains, as well as significant difficulty in fabrication when the wavelength shifts to the visible region. In this work, based on the polarization degree of freedom, we first, to the best of our knowledge, demonstrate high-fidelity (~0.98) single-photon transmission and distribution of entangled photons over a conjoined-tube hollow-core fibre (CTF) by using commercial silicon single-photon avalanche photodiodes. Our CTF realized the combined merits of low loss, high spatial mode purity, low polarization degradation, and low chromatic dispersion. We also demonstrate single-photon low latency (~99.96% speed of light in vacuum) transmission, thus paving the way for extensive uses of HCF links in versatile polarization-based quantum information processing.